In a conventional bindery line, signatures to be included in a book are selected and gathered. In one form, known as perfect or square-back binding, the gathered signatures are stacked on a conveyor. A flat cover sheet is placed around the gathered signatures and parallel creases or breaks are formed in the cover sheet to provide a square backbone. The distance between the breaks is determined by the thickness of the gathered signatures.
One known apparatus for forming such breaks is a cover breaker. The cover breaker includes a pair of spaced, planer movable plates. Specifically, the plates are reciprocally movable a preselected, fixed distance. When a covered and gathered signature, as discussed above, is positioned at the cover breaker, the plates move towards one another to flatten the cover sheet against the outermost signatures to break the cover, i.e, form the creases, and provide the square backbone.
With such a known cover breaker, the relative spacing between the plates can be manually adjusted according to the thickness of the gathered signatures. Specifically, a hand wheel is turned to adjust the relative positioning of the plates. Such a cover breaker operates satisfactorily in applications where a constant thickness is required over extended periods of time. However, such a cover breaker does not lend itself to more automated flat gathering systems wherein the thickness of any two consecutive books may be different. For example, with certain magazines or catalogs, different signatures, or more or less signatures, may be included according to the intended recipient.
The present invention is intended to overcome these and other problems associated with cover breakers.